MorningLightMountain is a Prime alien, the only immotile Prime on the original Prime world. It launched a genocidal war against the Commonwealth (i.e., humans), described in Pandora's Star and Judas Unchained.
The Primes were a genocidal species of aliens that wiped out all other life on their planet, so that they would not have to compete for resources with other species. They were pragmatic and emotionless, with regard for no life other than their own.
Each Prime Immotile was a being that mentally controlled ‘herds’ of Motiles, a subspecies that possessed little mental capacity. The Immotiles would create group clusters of their own Immotiles to expand their mental capacities and enable control of larger groups of Motiles. Immotile intelligences warred against one another all throughout their history, in a bid to wipe out the other group clusters.
Morninglightmountain was the dominant Prime throughout most of their history and ultimately destroyed the others. It used wormhole technology, obtained from the human Dudley Bose, and nuclear warheads to destroy other Immotiles. By opening a wormhole and dropping a warhead through, Morninglightmountain emerged as the only Prime life in its solar system, Dyson Alpha.